Nanoporous alumina (γ- and α-phase) gel cast thick film for the development of trace moisture sensor

In this study, erbia (Er₂O₃)-doped Bi₂O₃ ceramics were prepared from sol–gel derived nanocrystalline powders. The morphological properties were investigated by scanning electron microscopy. X-ray diffraction (XRD) analysis was carried out in order to characterize the phase and crystal structure of the powder samples. Temperature dependent electrical properties were determined by thermogravimetry/differential thermal analyzer (TG/DTA) and 4-point probe techniques. The stable fluorite face centered cubic δ-type phase was observed at room temperature from the XRD result, which was supported by the DTA and temperature dependent electrical conductivity measurements. Electrical conductivity results indicate that there is a transition approximately at 650 °C, which can be attributed to an order–disorder transition (ODT). The activation energy values obtained from the Arrhenius approach for heating and cooling process were presented. Two regimes, corresponding to high temperature region (HTR) and low temperature region (LTR), were observed. As a result of morphological changes during the ODT, the electrical conductivity modifies and the activation energies are different for studied sample at HTR and LTR.     

Utility of Japp-Klingemann reaction for the preparation of 5-carboxy-6-chloroindole via Fischer indole protocol

5-Carboxy-6-chloroindole, a precursor for p38 kinase inhibitor, was prepared from 4-amino-2-chloro-3-iodobenzoicacid by following the Japp-Klingemann synthetic approach. The structures of the key intermediates were also confirmed by X-ray analyses. Computational analysis was helpful in understanding the importance of the substituents at the cyclization step of the synthesis.     

Probabilities for radiative vacancy transfer from Li (i=1, 2, 3) sub-shells to the M, N and higher shells for elements with 77≤Z≤92

The probabilities for transfer of the L_i (i=1, 2, 3) subshell vacancy to the M, N and higher shells through radiative decay, ηLiJ(R), have been deduced for the elements with 77≤Z≤92 using the measured L X-ray production cross-sections at (i) the 59.54 keV γ-rays such that BL₁<Einc<BK and (ii) the K X-rays of a suitable secondary target chosen such that BL₃<EKα<BL₂ and BL₁/L₂<EKβ<BK; where BK/Li is the K shell/L_i subshell ionisation threshold of the target element. The deduced probabilities are compared with those calculated using the radiative and nonradiative transition rates based on the Dirac-Fock (DF) and the relativistic Dirac-Hartree-Slater (RDHS) calculations, respectively.     

Hollow microcapsules built by layer by layer assembly for the encapsulation and sustained release of curcumin

Hollow microcapsules fabricated by layer-by-layer assembly (LbL) using oppositely charged polyelectrolytes have figured in studies towards the design of novel drug delivery systems. The possibility of loading a fair amount of active component of poor aqueous solubility is one of the encouraging factors on the wide spread interest of this emerging technology. Curcumin has potent anti-cancer properties. Clinical application of this efficacious agent in cancer and other diseases has been limited due to poor aqueous solubility and consequently minimal systemic bioavailability. LbL constructed polyelectrolyte microcapsules based drug delivery systems have the potential for dispersing hydrophobic agent like curcumin in aqueous media. Here we report the preparation of LbL assembled microcapsules composed of poly(sodium 4-styrene sulfonic acid) and poly(ethylene imine) one after another. The microcapsules were characterized using various analytical techniques. Curcumin was encapsulated in these microcapsules and the efficacy of the released curcumin was studied using L929 cells.     

Tensile strength of aluminium nitride films

Two-layered aluminium nitride (AlN)/silicon nitride microbridges were fabricated for microbridge tests to evaluate the elastic modulus, residual stress and tensile strength of the AlN films. The silicon nitride layer was added to increase the robustness of the structure. In a microbridge test, load was applied to the centre of a microbridge and was gradually increased by a nano-indenter equipped with a wedge tip until the sample was broken, while displacement was recorded coherently. Measurements were performed on single-layered silicon nitride microbridges and two-layered AlN/silicon nitride microbridges respectively. The data were fitted to a theory to derive the elastic modulus, residual stress and tensile strength of the silicon nitride films and AlN films. For the AlN films, the three parameters were determined to be 200, 0.06 and 0.3?GPa, respectively. The values of elastic modulus obtained were consistent with those measured by conventional nano-indentation method. The tensile strength value can be used as a reference to reflect the maximum tolerable tensile stress of AlN films when they are used in micro-electromechanical devices.     

EPR,optical and superposition model study of Mn2+ doped L+ glutamic acid

Electron paramagnetic resonance (EPR) study of Mn²⁺ doped L+ glutamic acid single crystal is done at room temperature. Four interstitial sites are observed and the spin Hamiltonian parameters are calculated with the help of large number of resonant lines for various angular positions of external magnetic field. The optical absorption study is also done at room temperature. The energy values for different orbital levels are calculated, and observed bands are assigned as transitions from ⁶A_1g(s) ground state to various excited states. With the help of these assigned bands, Racah inter–electronic repulsion parameters B = 869 cm^?1, C = 2080 cm^?1 and cubic crystal field splitting parameter Dq = 730 cm^?1 are calculated. Zero field splitting (ZFS) parameters D and E are calculated by the perturbation formulae and crystal field parameters obtained using superposition model. The calculated values of ZFS parameters are in good agreement with the experimental values obtained by EPR.     

Effect of annealing conditions on high temperature superconductivity in La2−xSrxCuO4

Abstract

Besides investigating a number of oxides of the series La_2?xM_xCuO₄ (M=Ba, Pb, Sr), we have, in this investigation emphasised on the studies of the effect of annealing conditions on superconducting properties of composition La_1.8Sr_0.2CuO₄. The effect is remarkable and is di'scuss'ed in the light of X-ray diffraction results. These samples, studied after a gap of two months, showed interesting changes which has been discussed in the present paper.     

Structural,thermal, and spectral characterization of the different crystalline forms of Alq3, tris(quinolin-8-olato)aluminum(III), an electroluminescent material in OLED technology

The interest in organic materials for use in organic light-emitting diodes (OLEDs) began with the pioneering report of efficient green electroluminescence from Alq₃, tris(quinolin-8-olato)aluminum(III), by Tang and Van Slyke [C.W. Tang, S.A. Van Slyke, Appl. Phys. Lett. 51 (1987) 913]. After more than 20 years of intense research and development in OLEDs, Alq₃ continues to be a widely used electroluminescent material in OLED technology. Alq₃ is used in the electron-transport and/or electron-injecting layer in multilayer device structures and also as an effective host material for various dyes. Much is known about the properties of this metal chelate complex, yet much remains unknown despite numerous studies. In recent years, five crystalline phases (α, β, γ, δ, and ε) of Alq₃ have been identified. In the present report, a combined structural, thermal, and spectroscopic (Raman, fluorescence, and nuclear magnetic resonance) analysis of different crystalline phases of Alq₃ is presented.